The primary objective of the study is to assess the safety, tolerability, and antiviral activity of ABT-378/ritonavir when administered orally in a group of approximately eight antiretroviral naive HIV-infected patients. There are 3 secondary objectives: 1) To determine the steady-state pharmacokinetic profile of ABT-378/ritonavir in antiretroviral naive HIV- infected patients; 2) to characterize the HIV RNA decay profiles of ABT-378/ritonavir in antiretroviral naive HIVinfected patients; and 3) to assess the relationship between ABT-378/fitonavir phamacokinetics and HIV RNA decay profiles in antiretroviral naive HIV-infected patients. In this protocol, patients are required to come to the GCRC for directly observed dosing of ABT378/ritonavir for the morning dose only during the first two weeks of therapy. EKGs and vital signs are performed on days 1, 5,9, and 14. Zero-hour PK sampling is done on days 1,4,7, 1 0, and 14. Blood for other laboratory evaluations (CBC, chemistry, flow cytometry, HIV-I RNA, etc.) is drawn at screening and on study days - 1, 4,5,7, 1 0, and 14. Patients are monitored for adverse events by the study coordinator on a daily basis during the first 14 days of the study, and at regularly scheduled visits thereafter. 12-hour pharmacokinetic studies are done on the CRU at week 3, week 6, and at 6 months. Two nucleoside reverse transcriptase inhibitors, stavudine and lamivudine, are added to the treatment regimen on day 22. Patients are seen for zero-hour PK sampling and routine lab work at week 4, 6, 8, 10, 12, 16, 20, 24, 36, 48, and 52. Physical examinations are performed at day -1, day 28, week 8, 12, 16, 20, 24,36, 48, and 52.